factsheet no:4

Smoking and cancer

Action on Smoking and Health – August  2005

Introduction

It is estimated that one in three people will develop cancer at some stage in their lives and that one in four will die from the disease.[1]  In 2000, there were 42,800 cancer deaths in the UK attributable to smoking: approximately a third of all cancer deaths. [2]  The UK Government has set a target (for England) to reduce the cancer death rate in people aged under 75 by 20% by 2010. [3] The route to achieving this is set out in the National Cancer Plan which includes targets to reduce smoking.[4]  Cigarette smoking is an important cause of cancers of the lung, larynx (voice box), pharynx (throat), oesophagus, bladder, kidney and pancreas.  A recent review by the International Agency for Research on Cancer found that, in addition to these cancers, smoking is a cause of cancer of the nasal cavities and nasal sinuses, stomach liver, cervix and myeloid leukaemia.[5]

Lung cancer

Lung cancer is the most common cancer in the world with 1.2 million new cases diagnosed every year. [6] Until recently, lung cancer was the most frequently occurring cancer in the UK; it has now been overtaken by breast cancer but it still accounts for 1 in 7 new cancer cases, that is, around 38,400 new patients annually.  In Britain, one person every fifteen minutes is diagnosed with lung cancer.  Lung cancer is the cancer most commonly associated with smoking: around 90% of all lung cancers are caused by smoking, either directly or through indirect exposure.  Because of its poor prognosis, lung cancer is still the most common cause of cancer death in the UK, with around 33,600 deaths each year, accounting for 6% of all deaths and 22% of all cancer deaths in the UK. 6    

One in two smokers dies prematurely: of these, nearly one in four will die of lung cancer.  The risk of dying from lung cancer increases with the number of cigarettes smoked per day, although duration of smoking is the strongest determinant of lung cancer in smokers.  (See also Factsheet 5 in this series, Smoking & Respiratory Disease). Smokers who start when they are young are at an increased risk of developing lung cancer.  Results of a study of ex-smokers with lung cancer found that those who started smoking before age 15 had twice as many cell mutations as those who started after age 20.[7] 

A longitudinal study of British doctors by Doll and Peto examined the effects of prolonged cigarette smoking and prolonged cessation on mortality from lung cancer.[8]  They found that if people who have been smoking for many years stop, even well into middle age, they avoid most of their subsequent risk of lung cancer. Also, stopping smoking before middle age avoids more than 90% of the risk attributable to smoking.  

Cancers of the mouth and throat

Smoking cigarettes, pipes and cigars is a risk factor for all cancers associated with the larynx, oral cavity and oesophagus.  Over 90% of patients with oral cancer use tobacco by either smoking or chewing it. The risk for these cancers increases with the number of cigarettes smoked and those who smoke pipes or cigars experience a risk similar to that of cigarette smokers. In total, 4400 new cases of oral cancer were recorded in 2001s.[9] (“Oral cancer” includes cancers of the lip, tongue, mouth and throat.)  (See also: ASH briefing Tobacco and Oral Health)

Heavy smokers have laryngeal cancer mortality risks 20 to 30 times greater than non-smokers.14 People who drink alcohol and smoke have a much higher risk of oral and pharyngeal (throat) cancers than those only using tobacco or alcohol.  A US study revealed that among consumers of both products the risk of these cancers was increased more than 35-fold among those who smoked forty or more cigarettes a day and took more than four alcoholic drinks a day.   It has been estimated that tobacco smoking and alcohol drinking account for about three quarters of all oral and pharyngeal cancers.[10]

Bladder cancer

Tobacco smoking is the principal preventable risk factor for bladder cancer in both men and women. It is estimated that current smokers are two to five time more likely to develop bladder cancer than non-smokers.  As for lung cancer, the risk is associated with both the dose and duration of smoking, while cessation of smoking reduces the risk.[11]  

Breast cancer

Some studies have demonstrated a link between both active and passive smoking and breast cancer. The IARC review concluded that most epidemiological studies have found no association between active smoking and breast cancer but since its publication a new study found that among women who had smoked for 40 years or longer the risk of breast cancer was 60% higher that that of women who had never smoked. Among those who smoked 20 cigarettes or more a day for 40 years, the risk rose to 83%.[12] 

Cervical cancer

Cancer of the cervix has been found to be associated with cigarette smoking in many case-control studies. Until recently, scientists had been unable to decide whether the relationship was causal or due to confounding factors such as the number of sexual partners.   A study in Sweden investigated whether environmental factors such as smoking, nutrition and oral contraceptive use were independent risk factors for cervical cancer and found that smoking was the second most significant environmental factor after human papilloma virus (HPV).[13]  The IARC review concludes that there is now sufficient evidence to establish a causal association of squamous-cell cervical carcinoma with smoking.5  

Colorectal cancer

 According to the IARC review, there is some evidence that the risk of colorectal cancer is raised among tobacco smokers.  However, it is not possible to conclude that smoking is a cause of colorectal cancer.  This may be due to inadequate adjustment for confounding factors which could account for some of the small increase in risk that appears to be associated with smoking.5   

Kidney cancer

Kidney cancer has consistently been found to be more common in smokers than in non-smokers and there is now sufficient evidence to show that smoking is a risk factor for the two principal types of kidney cancer. [14]  There is a dose-response relationship with increasing numbers of cigarettes per day and risk appears to drop after smoking cessation.  Approximately 24% of kidney cancer cases in men and 9% in women can be attributed to smoking. [15]  

Leukaemia

Smoking is causally associated with myeloid leukemia in adults but not to lymphoid leukemia. [16]   A  French study of patients with newly diagnosed acute myeloid leukemia concluded that cigarette smoking had an adverse effect on survival in acute myeloblastic leukemia (AML), by shortening complete remission duration and subsequent survival. [17]

Liver cancer

Large case-control studies have demonstrated an association between smoking and risk of liver cancer. In many studies,  the risk increases with duration of smoking or number of cigarettes smoked daily.  Confounding from alcohol can be ruled out in the best case-control studies, by means of careful adjustment for drinking habits.  As association with smoking has also been demonstrated among non-drinkers.  The IARC review concludes that “there is now sufficient evidence to judge the association between tobacco smoking and liver cancer as causal”.5

Oesophageal cancer

Tobacco smoking is a cause of cancer of the oesophagus (gullet) and the risk increases with the number of cigarettes smoked and duration of smoking.  The risk also remains elevated many years after smoking cessation.5

Pancreatic cancer

Cancer of the pancreas is a rapidly fatal disease with a five‑year survival rate of only 4%.  Cigarette smoking is a strong and consistent predictor of pancreatic cancer although the risk diminishes to that of a non-smoker ten years, on average, after cessation.  Risk of the disease is related to consumption and duration of smoking.  Smokers have about twice as high a risk for this cancer as non-smokers. 5

Stomach cancer

Studies have shown a consistent association between cigarette smoking and cancer of the stomach in both men and women.  Risk increases with duration of smoking and number of cigarettes smoked, and decreases with increasing duration of successful quitting. 5   

Passive smoking

Non-smokers are at risk of contracting lung cancer from exposure to other people's smoke.  The UK's  Scientific Committee on Tobacco and Health (SCOTH) found that the research findings were consistent with an increased risk of lung cancer in non-smokers of between 20% and 30%.[18]  A subsequent review of the evidence by SCOTH in 2004 re-confirmed that the increased risk was in the order of 24%. [19]  This means that passive smoking causes several hundred lung cancer deaths in non-smokers each year in the UK.  The IARC review confirmed that “the evidence is sufficient to conclude that involuntary smoking is a cause of lung cancer in never smokers.   (For further information see Factsheet No. 8, Passive Smoking or the more detailed Passive smoking briefing.)